Since 1976, the Toronto group has been a member of the Lung Cancer Study Group (LCSG). To date, all studies so far activated are in patients with potentially recectable, non-small cell carcinoma of the lung. In every study except the one most recently activated (821), the value of adjuvant therapy following surgical resection has been tested in a controlled, randomized fashion. To date, studies have included adjuvant immunotherapy, chemotherapy and radiation, or combinations of these modalities. In order to carry out these studies, a multidisciplinary staff is available at each of the centres, including Toronto. We are presently entering patients on all activated studies, including 771, 772, 791, 801 and 821. Data are collected and sent to the Operations Office in the Washington area for analysis. Pathology is confirmed at a reference centre in Houston, Texas. Further studies will involve the same population but, in addition, be expanded to include patients with small cell carcinoma of the lung, as well as some patients with unresectable, non-small cell lung cancer. In small cell lung cancer, the value of surgery in addition to chemothereapy will be studied. Pilot studies are underway to determine the feasibility of giving chemotherapy and radiation in patients with unresectable, non-small cell lung cancer, followed by attempted resection in those who respond. Evaluation of the quality of life of patients in LCSG studies is of top priority. In the most recently activated study, the value of limited sugical resection is being tested. In the future, we will apply all new ideas that become available for the treatment of lung cancer and test them in a clinically controlled manner to determine their relative value.